You can pinch the feather stem on the backside every 1/8 inch. Pinch it between your thumbnail and index finger. Dig your thumbnail into it a little. I also have a pair of non serrated flat pliers that I flatten the stems at the tie in section. This gives me much more accuracy in getting the feathers to lay straight out instead of rolling one way or the other. Works great for tying in feathers for tails too. Bass bugs or saltwater flies.
Bob